Environmental Justice

Environmental Legacy of redlining



  What is the present-day impact of historic “redlining” of US cities during the Great Depression on ecological processes?

Environmental Justice and Ecology

screenshot of Schell et al paper

picture of Dr. Christopher Schell Dr. Christopher Schell

Environmental Justice and Ecology

Figure 1a from Schell et al.

https://doi.org/10.1126/science.aay4497

Context: Redlining

  • The Home Owners’ Loan Corporation (HOLC) was a government-sponsored corporation created as part of the New Deal
  • The HOLC created a housing appraisal system of color-coded maps that categorized the riskiness of lending to households in different neighborhoods
  • Lower grades = less opportunity for loans but lower grades also = minority communities
  • Red-lining: A discriminatory practice in which financial services are withheld from neighborhoods that have significant numbers of racial and ethnic minorities
  • It was outlawed in 1968 following the passage of the civil rights bill.

Data: Mapping Relining

  • Mapping Relining is a project at the University of Richmond that provides maps of HOLC grades in cities across the U.S.

  • Maps are available as polygons for use in geospatial analysis

Context: Canopy cover

  • Trees and vegetation influence the local temperatures
  • Generally: more trees/canopy, cooler local temperatures

diagram of influence of forests on temperature

Data: satellites

Vegetation indices from satellites

Sentinel 2

  • 10 m, 20 m and 60 m spatial resolution

  • Since 2015

  • Maps every 10 days

image of satellite

Data: Satellites

  • Satellites record reflected light in different regions of the light spectrum (wavelengths)

  • Data = a value of average intensity over a window of wavelengths (“band”)

  • Bands are chosen because they measure different aspects of the environment.

Data: Satellites

diagram of spectral bands measured by Sentinel 2

Data: Indices

  • Bands can be combined to get indices that measure ecological processes
  • Normalized Difference Vegetation Index (NDVI) ~ photosynthesis (amount + health of vegetation)
  • Higher NDVI = more canopy = cooler local temperatures

diagram of NDVI calculation

Data: Raster

Band and NDVI across space are stored as rasters

diagram of a raster

Data: Data Cubes

Rasters are combined over time to form data cubes

diagram of a raster cube

Data: COGs and GeoTIFFs




Full remote sensing data sets are huge! (many bands, locations, times)

Data: COGs and GeoTIFFs

  • A Cloud Optimized GeoTIFF (COG) is a regular GeoTIFF file aimed at being hosted on an HTTP file server with an internal organization that enables more efficient workflows on the cloud.
  • Leverages the ability of clients to request just the parts of a file they need. (https://cogeo.org)
  • GeoTIFF is a public domain metadata standard that allows georeferencing information to be embedded within a TIFF file (https://en.wikipedia.org/wiki/GeoTIFF)

Environmental Justice and Ecology

NDVI for different grades from Figure 2 in Schell et al.

Assignment

  • Calculate, map, and analyze NDVI for different redlining grades within Richmond, VA
  • Calculate and map NDVI for different redlining grades for five cities of your choice
  • Evaluate how the relative influence of redlining varies across environmental or demographic gradients

Assignment

  • Review tutorial env-justice-tutorial.qmd
  • Assignment is in assignment/env-justice.qmd

Data Science Skills

  • Cloud access of remote sensing data
  • Raster Cubes
  • Linking rasters with polygons
  • Calculating spatial statistics within polygons.